Field-magnet pole



UNITED STATES PATENT OFFICE.

JAMES J. IVOOD, OF FORT IVAYN E, INDIANA.

FIELD-MAGNET POLE.

SPECIFICATION forming part of Letters Patent No. 571,181, dated November10, 1896.

Application filed September 8, 1896. Serial No. 605,154. N model.)

To all whom it may concern.-

Be it known that I, JAMES J. Ween, a citizen of the United States,residing in Fort \Vayne, in the county of Allen and State of Indiana,have invented certain new and use ful Improvements in Field-MagnetPoles, of

which the following is a specification.

This invention relates to the construction of field-magnets for electricmachinery having poles of laminated iron embedded in castiron yokes orcrowns. Snell laminated poles require to be embedded for a considerabledepth in the cast yoke, in order to give sufficient mechanical strengthto their connection, and also to provide sufficient contact-surfacebetween the wrought-iron and east-iron to avoid choking the lines ofmagnetic force, it being well known that a given cross-section ofwrought-iron is capable of carrying twice as many lines of force as thesame cross-section of cast-iron.

The objects of the present invention are to avoid the weakening of thecast yoke or crown where the cast metal is displaced by the embedment ofthe laminated pole in it, thereby avoiding the necessity of thickeningthe cast metal at this point,in order thereby to preserve sufficientmechanical strength; second, to increase as much as possible thecontact-surface between the wrought-iron and cast-iron, in order toprevent choking of the lines of magnetic force at their contact, andthereby introducing a wasteful resistance in the magnetic circuit;third, to reduce the amount of wrought-iron required and avoid wastethereof; fourth, to reduce the amount of copper required to excite thefield at a given density, and, fifth, to reduce the cost of the machine.To these ends my invention introduces the novel construction shown inthe accompanying drawings, wherein Figure 1 is a perspective viewshowing the laminated pole with the cast yoke or crown broken away toshow the construction of the pole. Fig. 2 is a perspective of one of theplates or laminae of which the pole is built up. Fig. 3 shows two platessuperposed and reversed. Fig. 4c shows one of the wrought-ironpunchings, which by being out across on the dotted line forms two of thepole plates or laminae. Fig. 5 is a fragmentary section showing theold-style construction upon which my invention is most directly animprovement, Fig. 6 being a transverse section there of on the line 0 6.Figs. 7 and 8 are sectional views corresponding to Figs. 5 and 6 andillustrating my improved construction, the plane of Fig. 8 being on theline 8 8. Fig. 9 indicates two punchings or plates of the oldconstruction shown in Fig. 5, the tinted portion indicating the metalwhich is saved according to the construction introduced by my invention.Fig. 10 is a fragmentary view of a modified form of plate.

I will first describe the old construction shown in Figs. 5 and (5. Theplates or laminae are punched out with the outlines shown in Figs. 5 and9, with half-round notches Z) Z) on opposite sides of the root orembedded portion of the pole, and the plates being piled together inalinement, so as to form a block constituting the pole, these notchescoinciding with one another, so as to form grooves or channels onopposite sides of the root of the pole, as indicated in Fig. 6. Theplates are joined together in a solid block by means of pins 0, passingthrough coinciding holes and riveted down on the ends. The block orpolepiece A thus built up is placed in the mold, and the yoke or crown Bof east-iron is cast around it, the cast-iron filling the channels I) Z)and forming thereby a dovetail connection by which the embedded portionof the pole is firmly united with the yoke. In order to afford asufficient surface of contact, and also a sufliciently-strong mechanicalconnection between the pole and the yoke, the pole is embedded in theyoke to such depth as to occupy a considerable proportion of thecrosssection of the cast metal, thereby notably weakening the latter ornecessitating that it be strengthened by increasing its crosssection.

According to my improved construction I form the root or embedded end ofthe pole with oblique ribs recurring at intervals and alternated withoblique channels to the effect best shown in Fig. 1. To this end thepole is made up of punchings or laminze a a, one of which is shown inFig. 2 and the outline of which is shown in Fig. 3. Several. of theseplates (four, for example, more or less) are superposed in coincidence;then an equal number are superposed but reversed relatively to the firstgroup, as shown in Fig. 3 then a third group is built up and placed incoincidence with the first group, and so on, each alternate group beingreversed relatively to that which precedes it until the entire widthdesired for the pole is thus built up. It will be seen that the upperend (1 of each plate or punching is cut obliquely, so that, as seen inFig. 7, the embedded portion of the lamina is of unequal length at itsoppo site sides. The laminae have the same notches or recesses b as inthe old construction, with the difference that these notches appear ononly one side of each of the laminze, the one on the other beingeliminated by reason of the obliquity of the top d. It results that in abuilt-up pole the embedded end or root thereof consists of a series ofoppositely-inclined dovetails or ribs, the channels formed by thecoincident notches Z1 being discontinuous. The entire block ofsuperposed laminze is held together by rivetpins 0 c, as formerly.

The pole A having been built up as thus described is placed in the mold,and the yoke B is cast upon it. I have shown only one pole and afragment of the yoke, but in practice there are always two poles or amultiple of two, as is understood. The preferred extent of embedment ofthe pole in the cast yoke is clearly indicated in Fig. 7. In casting,the cast metal flows into all the spaces between the projecting ribs ordovetails of the core, thus forming a rib of cast metal wherever thereis a channel or space between two of the laminated ribs or dovetails ofthe core. It results that the cast-iron resolves itself into a series ofobliquely-crossing ribs. The existence of these ribs enormouslyincreases the strength of the yoke or crown, which actually appearsunder test to be as strong as if both yoke and pole were of solidcast-iron. The several ribs, by crossing each other and interlocking inthe manner shown, produce a very strong and rigid construction, whilethe cast metal in the act of shrinking presses the laminze into theclosest contact, making a most perfect joint. By the flowing of the castmetal into the channels or spaces be tween the projecting ribs ordovetails the contact-surface between the cast and wrought metal isgreatly increased as compared with the old construction.

In the old construction (shown in Figs. 5

and 6,) the yoke is much weakened by the embedment of the pole in it,the gain in strength of the yoke being perceptible at a glance bycomparing Figs. 6 and 8. In the old construction the shrinkage of themetal does not tend to make as good a contact, since the part of theyoke in contact with the wrought-iron is not supported by ribs of castmetal extending across from side to side and tending to hold it in closecontact. On the contrary the form of its shrinkage tends to spring itaway at the lower edge and thereby weaken the crown mechanically whileimpairing the magnetic conductivity.

Fig. 4 shows how the punchings are cut out in pairs, forming no wasteexcept where the notches Z) Z) occur, and the waste due to these isreduced one half, since each punching has only one notch instead of two.The punchings are afterward cut apart upon the dotted line.

Fig. 9 shows the saving in wrought metal by my improved construction ascompared with the old style, the tinted portion indicating the metalsaved. The figure shows two of the old-style punchings placed togetherhead to head, whereupon by severing each. one on the oblique line it isconverted into my improved punching. The space of the wrought-ironsaved, as shown by the tinted portion, is in my improved construction0ccupied by the cast-iron oi the yoke, thereby correspondinglystrengthening the yoke.

Fig. 10 shows a slight modification, the top of the punching beingformed with a reverse curve instead of an oblique straight line, a

diiference, however, which is immaterial, the' construction firstdescribed being preferred.

The lamina) may be of greater orless thickness, as desired, and more orless of them may be grouped together to form the successive groupsconstituting the alternate right and left hand dovetail-ribs.

My invention might even be modified to the extent of alternating eachsuccessive punching or lamina, especially if the lamime were ofconsiderable thickness, but this is not recommended.

I claim as my invention the following defined novel features orimprovements, substantially as hereinbefore specified, namely:

1. A field-magnet having a cast yoke and laminated poles embedded in it,said poles made of lamina: having sides of unequal length at theirembedded ends, and said laminse reversed at intervals to form obliqueribs projecting to alternately opposite sides, so that oblique spacesare left between them which are filled with ribs of cast-iron, servingto stren then the yoke and increase the area of surface-contact betweenthe wrought and cast iron.

2. A laminated field-pole adapted at one end to be embedded in a castyoke made of laminze having sides of unequal length at their embeddedends, and reversed at intervals to form oblique ribs projecting toalternately opposite sides, so that the embedded end of the polepresents an alternation of oppositely-inelined ribs with inclinedchannels between them.

A lamina or punching for a field-magnet pole, having its end (Z formedwith an oblique outline so as to be longer on one side than the other,and with a notch 11 formed in the longer side.

In witness whereof I have hereunto signed my name in the presence of twosubscribing witnesses.

.liiitiltS Li. WOOD.

\Vitnesses:

CHARLES C. .hIILLlGl-t, M. 0. Guess.

